The present invention relates to a typewriter having a calculating function or arithmetic capability, which is capable of not only printing a succession of characters including letters, numerals and arithmetic symbols selected by corresponding keys on the keyboard, but also performing an arithmetic operation designated by an arithmetic symbol key and printing a result of the operation following the keyed-in characters, the arithmetic operation being performed based on numeric data entered through numeral keys on the keyboard.
In a typewriter having a calculating function known in the art, there are available two different modes of operation: a printing mode for printing a succession of characters such as letters, numerals and arithmetic symbols selected by the keyboard keys; and an arithmetic operation mode for performing a mathematical operation defined by an arithmetic operator represented by an arithmetic symbol key and by numeric data entered as operands through numeral keys. In such prior art typewriter, however, there is a recognized drawback in the printing mode that although it is possible to print numerical values followed by a letter or letters to identify the meaning of such values in combination with an arithmetic operator designating symbol or symbols, it is impossible to perform an arithmetic or mathematical operation given by the arithmetic symbol and numerical values followed by identifying letters, and therefore impossible to print the result of operation within a line of statements including letters, numerical values and arithmetic symbols. In the arithmetic operation mode, there is another drawback that no letters are allowed to exist within an arithmetic equation consisting of numerical values and an arithmetic symbol or symbols. In other words, it is not possible to print an arithmetic equation including letters for identifying the numerical values given as operands.